The present invention relates to the electron beam technique, and in particular, to an electron beam apparatus such as an inspection apparatus, a microscope, etc. used in the semiconductor process, etc.
In the semiconductor process, a variety of kinds of electron beam apparatus are used with the aim of the observation of the circuit pattern formed on the wafer and the chip, the measurement, the defect review and classification, the inspection, etc. In these electron beam apparatus, the above-mentioned observation, measurement, defect review and classification, inspection, etc. are conducted by irradiating an electron beam called a primary beam on a sample and performing a variety of kinds of operation process for a signal obtained by detecting a secondary electron and a reflected electron, etc. which was generated.
In the above-mentioned apparatus with the aim of any one of the observation, the measurement, the defect review and classification, and the inspection, the improvement of the precision of the defect detection and the measurement is the important subject. As the detection precision of the secondary electron and the reflected electron is greatly affected by the surface charged state of the surface of the sample, in order to conduct the high precision inspection and measurement, the surface charge control of the surface of the sample is important.
For example, in JP-A-10-294345, it is disclosed an invention which controls the surface charged state of the sample by providing a preliminary electron source for irradiation other than an electron source for the primary electron beam and irradiating the electron beam irradiated from said preliminary electron source for irradiation on the sample. On the other hand, in JP-A-2002-524827, it is disclosed an invention which controls the surface charged state of the sample by scanning the primary electron beam on the sample. In the invention disclosed in said document, the surface charge control and the image acquisition by the same beam are made to be possible by shifting the irradiation of the electron beam for image-forming and the electron beam for surface charge control timewise. Also, in JP-A-10-339711, it is disclosed an electron beam apparatus which splits the electron beam into two using a biprism and irradiates one for surface charge control and the other for the inspection on the sample. As it irradiates the primary beam separately, the space between the irradiation position of the electron beam for inspection and the irradiation position of the electron beam for surface charge control can be made to be smaller than the preliminary irradiation method as disclosed in JP-A-10-294345, therefore it has an advantage that the time lag from the irradiation of the electron beam for surface charge control to the irradiation of the electron beam for image formation can be reduced.
On the other hand, in the electron beam apparatus, as well as the precision of the measurement and the inspection, it is also important to improve the execution rate of the above-mentioned observation, measurement, defect review and classification, inspection, etc., namely the throughput. The simplest method to improve the throughput is to make the area of the region from which the secondary electron/reflected electron is detected per unit time as large as possible while securing the detection amount of the secondary electron/reflected electron with which the signal amount necessary for the inspection and the measurement can be secured. For this reason, a variety of electron beam apparatus have been proposed such as a multicolumn method which detects the signal by scanning a plurality of electron beams simultaneously and in parallel on the sample using a plurality of electron beam columns, a collective irradiation image-forming method which obtains signals necessary for the detection and measurement by irradiating an area beam which has a certain wideness instead of a converged electron beam on the sample and collectively forming the image of the secondary charged particles which have been generated, etc. For example, in U.S. Pat. No. 6,914,441, an electron beam apparatus of multicolumn method is disclosed.